The present invention relates to belt tensioners, and in particular, belt tensioners which can be easily and precisely installed in operative relation with a timing or drive belt.
Belt tensioners, are, of course, well known devices that have been utilized in many belt systems heretofore. It is conventional practice in the belt tensioner art to provide for the application of a constant belt tensioning force which compensates for increases in belt length due to wear and other factors. A common type of conventional belt tensioner embodies a fixed structure and a pivoted structure pivotally mounted on the fixed structure by a pivot assembly. The pivoted structure carries a belt-engaging pulley. A coil spring is mounted in surrounding relation to the pivot assembly and has its ends connected between the fixed and pivoted structures so as to bias the latter toward a position of maximum belt take-up so that the spring biasing force decreases as the pivoted structure moves from a position of minimum take up to a position of maximum belt take-up. Despite this varying spring force within the range of movement provided, a substantially constant belt tension is maintained. The principles stated above can be appreciated from U.S. Pat. No. 4,473,362.
It is also known that when belt tensioners are installed on the engine, they should be installed so as to apply a predetermined static tensioning force to the belt. In addition, the pivoted structure which conventionally carries the pulley is movable between two positions defined by end stops. During the adjustment or installation of the tensioner, an adjusting eccentric member forming part of the fixed structure is adjusted to move the pivoted structure into a position between the stops, wherein the belt tensioning pulley is disposed in a predetermined static tensioning relation to the belt. Such arrangements are proposed in U.S. Pat. No. 5,244,438, and UK Patent No. 2,249,152.
A shortcoming in the designs of these two patents is that they both disclose tensioners that have a base plate on which the adjusting eccentric member is mounted. In this construction, wherein a base plate forms part of the tensioner and is used to mount the eccentric adjusting member onto a mounting surface for the engine frame, it is difficult to make certain that the eccentric adjusting member establishes a pivotal axis which is perpendicular to the engine frame with the desired degree of preciseness. This perpendicularity is desirable so that the tensioning pulley is not tilted, and so that the belt is axially balanced on the pulley.
It is an object of the present invention to provide a belt tensioner which has an eccentric adjusting member which is mounted directly onto the mounting surface provided for the engine, without a tensioner base plate therebetween.
In achieving this object, the present invention provides a belt tensioner for tensioning a drive belt or timing belt comprises an eccentric adjusting member having an end surface thereof constructed and arranged to be mounted directly in surface-to-surface engagement with respect to a belt tensioner mounting surface provided by an engine frame. A pivoted structure is mounted on the eccentric adjusting member for pivoted movement between a first position and a second position, and a belt tensioning pulley is mounted for rotational movement on the pivoted structure. A coil torsion spring is constructed and arranged to resiliently bias the pivoted structure in a belt tightening direction away from the first position and toward the second position, the eccentric adjusting member being movable during an installation procedure to move the pivoted structure against the bias of the coil torsion spring into a position wherein the belt tensioning pulley is disposed in predetermined static tensioning relation with the belt, at which point the eccentric adjusting member is to be manually fixed. The end surface of the eccentric adjusting member is in sliding surface-to-surface relation with the mounting surface during rotation of the eccentric adjusting member.
Furthermore, conventional tensioners provides a stop member which limits the amount of travel of the pivoted structure between the first and second positions. These stop members have heretofore been substantially rigid, so as to provide a significant amount of shock or impact to the pivoted structure when the stop is hit with a large force. It is an object of the present invention to provide a more resilient stop member to reduce severity of impact received by the pivoted structure upon reaching the first or second stop positions, without increasing the cost of the tensioner. To accomplish this, the coil torsion spring used to bias the pivoted structure in a belt-tightening direction towards the second position has an extending portion thereof used as a stop member.
In particular, the present invention achieves the above object by providing a belt tensioner for tensioning a drive belt or timing belt comprising an eccentric adjusting member constructed and arranged to be mounted on a mounting surface for an engine frame, and a pivoted structure mounted on the adjusting member for pivoted movement between a first position and a second position. The pivoted structure has first and second stop surfaces providing limits to the movement thereof. A belt tensioning pulley is mounted for rotational movement on the pivoted structure, and a coil torsion spring has one end thereof operatively connected with the pivoted structure and is constructed and arranged to resiliently bias the pivoted structure in a belt tightening direction away from the first position and toward the second position, the torsion spring having a radially outwardly extending second end. The eccentric adjusting member is adjustable during an installation procedure to move the pivoted structure against the bias of the coil torsion spring into a position wherein the belt tensioning pulley is disposed in predetermined static tensioning relation with the belt, at which point the eccentric adjusting member is to be manually fixed. During operation of the tensioner, movement of the pivoted structure in a direction toward the first position is terminated at the first position by engagement of the first stop surface with the radially outwardly extending second end of the coil torsion spring, and movement of the pivoted structure in a direction toward the second position is terminated at the second position by engagement of the second stop surface with the radially outwardly extending second end of the coil torsion spring.
Furthermore, during the installation procedure, the precise positioning of the pivoted structure relative to the stop surfaces is more critical than the positioning of the pivoted structure for purposes of placing the pulley in predetermined static tensioning relation with the belt, as the latter permits a greater margin of error. Thus, it is an object of the present invention to provide a belt tensioner wherein the position of the pivoted structure relative to the stop surfaces is fixed during the installation procedure in which the pulley is moved into predetermined static tensioning relation with the belt. After the predetermined tensioning relation of the pulley with the belt is established, the pivoted structure is released to permit relative movement thereof towards and away from the stop surfaces.
In particular, the above object is achieved by providing a belt tensioner for tensioning a drive belt or timing belt comprising an eccentric adjusting member constructed and arranged to be mounted on a mounting surface for an engine frame, and a pivoted structure mounted on the adjusting member for pivoted movement between a first position and a second position, the pivoted structure having first and second stop surfaces. A belt tensioning pulley is mounted for rotational movement on the pivoted structure, and a coil torsion spring is constructed and arranged to resiliently bias the pivoted structure in a belt tightening direction away from the first position and toward the second position. The eccentric adjusting member is adjustable during installation of the belt tensioner to move the pivoted structure against the bias of the coil torsion spring into a position wherein the belt tensioning pulley is disposed in predetermined static tensioning relation with the belt, the pivoted structure having an indicator being movable into a position indicating that the pulley is in the predetermined static tensioning engagement with the belt during the installation. A base plate provides first and second stop surfaces, the base plate being temporarily attached to the pivoted structure for movement therewith during the installation such that the first stop surface of the pivoted structure is disposed a fixed predetermined distance from the first stop surface of the base plate and the second stop surface of the pivoted structure is disposed a fixed predetermined distance from the second stop surface of the base plate during concurrent rotation of the pivoted structure and the base plate during the installation of the tensioner. The eccentric adjusting member and the base plate are constructed and arranged to be manually fixed from further movement after the belt tensioning pulley is moved into the predetermined static tensioning relation with the belt, and the tensioner is rendered operative after the base plate is fixed from further movement by unattaching the pivoted structure from the base plate to enable pivotal movement of the pivoted structure with respect to the eccentric adjusting member.
As a further object of the present invention, a spring extension from the coil torsion spring which biases the pivoted structure in the belt tightening direction is used as an indicator for indicating the appropriate installation of the tensioner.
In particular, the present invention provides a belt tensioner for tensioning a drive belt or timing belt comprising an eccentric adjusting member constructed and arranged to be mounted on a mounting surface for an engine frame. A pivoted structure is mounted on the adjusting member for pivoted movement between a first position and a second position, the pivoted structure having an indicator for indicating a relative position of the pivoted structure with respect to the first and second positions. A belt tensioning pulley is mounted for rotational movement on the pivoted structure. A coil torsion spring has one end thereof operatively connected with the pivoted structure and is constructed and arranged to resiliently bias the pivoted structure in a belt tightening direction away from the first position and toward the second position, the coil torsion spring having a radially outwardly extending second end. The eccentric adjusting member is adjustable during an installation procedure to move the pivoted structure into a position wherein the belt tensioning pulley is disposed in predetermined static tensioning relation with the belt. The pivoted structure is movable relative to the eccentric adjusting member and against the bias of the coil torsion spring during adjustment of the eccentric adjusting member so that the indicator is moved into alignment with the radially outwardly extending second end of the coil spring, thus indicating that the pulley has been moved into the predetermined static tensioning relation with the belt and that the pivoted structure has been moved to a predetermined static position relative to the first and second positions, at which point the eccentric adjusting member is to be manually fixed.
Other objects and advantages of the present invention will be appreciated from the following detailed description of the drawings and the appended claims.